The overall goal of the Boston Roybal Center for Active Lifestyle Interventions (RALI Boston) is to develop and test behavior change strategies to promote healthy aging, especially among sedentary adults and others at high risk for poor health outcomes. It is widely known that physical activity is broadly beneficial for physical, psychological, and cognitive aspects of health. However, the number of middle-aged and older adults who are regularly active remains quite low. This RALI Boston renewal application focuses on theme #2 from the RFA: ?Physical activity promotion to create, modify and pilot test principle-based interventions to reduce sedentary behavior and increase physical activity.? The specific aims of the project are to: 1) conduct innovative clinical trials based on solid research evidence and using the NIH Stage Model that can be translated to increase physical activity in middle-aged and older adults as a means to healthy aging, 2) advance research on behavior change processes in intervention research by identifying and testing the mechanisms that lead to increases in physical activity and improved health and well-being, 3) provide the necessary scientific expertise and resources to facilitate innovative interdisciplinary research and translation by leading and coordinating projects across five universities and community organizations. These aims will be accomplished through two cores, the Management and Administration Core and the Pilot Core. We will develop novel behavior change strategies, evaluate how they work in clinical trials with different vulnerable populations, and assess whether they lead to sustained changes in physical activity, using well-validated measures that are available to investigators in our RALI Toolbox. Ultimately, we will use the information gained to refine the techniques and update our conceptual framework, and will develop and test full scale translational interventions designed to improve activity, health and quality of life among middle-aged and older adults. The Center is distinguished by a number of innovative features: It 1) recognizes the multiple influences on human behavior that interact in complex ways and applies a unique multi-component model of behavior change; 2) uses a personalized approach and adapts the proposed interventions according to the individual characteristics and contextual circumstances of the person; 3) expands our focus to include basic neural mechanisms and other mediators of behavior change by employing novel imaging methods and noninvasive electrical stimulation; 4) focuses on underserved, vulnerable populations of middle-aged and elderly adults at risk for poor health outcomes and partners with community organizations serving diverse middle-aged and older adults who will benefit from the Center activities; 5) uses a common core of behavioral measures that will enable us to compare results of different pilot study interventions; 6) has successfully engaged a committed, interdisciplinary team of senior investigators who bring multiple professional perspectives and extensive resources from five universities: Brandeis U, Boston U., Boston College, Northeastern U., Harvard Medical School/Hebrew Senior Life.